Debunking Miller's Magic 7
Seven's a nice-enough number, but don't let it guide Web site design decisions.
George A. Miller penned a research paper in 1956, “The Magical Number Seven, Plus or Minus Two: Some Limits on Our Capacity for Processing Information.” It was groundbreaking in its time. In it, Miller hypothesized the human working memory can hold up to seven bits of information, plus or minus two, at once. Often referred to as “Miller’s Magic 7,” that theory is the basis of many Web page design decisions. Below, some modern day extrapolations and design conclusions rooted in Miller’s research:
- Give users only seven links (choices) in the active window.
- Give users only seven items on the menu bar.
- Give users only seven tabs at the top of a Web site page.
- Give users only seven items in a pull-down menu.
- Give users only seven items on a bulleted list.
Many advances have been made in understanding human memory since 1956. Why does Miller’s Magic 7 survive in light of current science? We can’t concede that maximizing this informational processing “capacity” is necessary on a Web site.
I want to offer a more current and commonsensical approach to these design element “conclusions.” No designer should be bound by a meaningless number rooted in dusty science.
The Boring Giants, Miller’s Laws’ Biggest Offenders
While studying the 16 top-selling Web sites recently, we wondered, “What do these sites all have in common?”
Our first response was, “They’re boring.” We also noticed something else.
With a few exceptions, each site had an extraordinary amount of hyperlinks on its home page.
As of this writing, Amazon.com has 24 links in the active window, not counting “Rate This” links, which would bring the total to 28. The left navigation menu sports almost 70 links in 12 categories. The search drop-down menu offers over 40 choices.
eBay’s home page gives users over 60 active window hyperlinks in 10 separate categories. The left nav bar holds offers over 40 choices.
Even sites with lighter numbers of hyperlinks, such as Dell.com (19 home page links) have significantly more links than the Magic 7 prescribed by Miller.
Seven May Be Magic, But It’s Not Science
Asked what my favorite number is, I might say, “Seven.” Seven is one of those magical numbers. It rolls nicely off the tongue and is much hipper than the stiff, inflexible five or the curvier, softer six and heftier eight. Yes, I like the number seven. But my devotion has nothing to do with Web design or online persuasiveness.
John S. Rhodes drills down into Miller’s article. Considering Apple’s lauded iPod has seven different user input points and phone numbers contain seven digits, it’s easy to buy into seven’s fallacy and allure.
Our capability to remember seven information chunks has little to do with a site’s usability or persuasiveness. Do you need to memorize a site’s interface to find the “Baby” section on Amazon or a digital camera on eBay? Search and standardized navigation elements make this moot.
Standards of a usable Web site should be measured in terms of meeting visitor needs and addressing their motivations with clear, well-placed, relevantly labeled menu items and site elements. In the active window, visitors should be able to scan and easily find links that entice them to click through. For clarification, here’s our definition of “usability”:
The ability to implement effectively the body of knowledge concerning the human-computer interface in order to remove any obstacles impeding the experience and process of online interactions.
Notice the absence of seven?
Limiting a visitor’s choices to seven menu items or seven active window links would be like Wal-Mart limiting the number of store aisles to seven. Miller’s research simply doesn’t correlate with a persuasive Web site design approach.
The Efficiency of the Human Mind
Ever bought a new car? As soon as you roll it off the dealer’s lot, you suddenly notice every other car like it.
“Where did all these come from? I never noticed them before,” you say.
Of course you didn’t. These cars weren’t as relevant before you bought your car. Now that you have one of your own, they’re top of mind.
When visitors arrive at your site, they don’t need to “remember” the site’s interface. They need to accomplish their goals. If they can easily see, find, and use the site to accomplish their goals, they’ll efficiently ignore the other available choices.
Menu items, navigation tabs, planned user paths, and other design elements shouldn’t be determined by a static number rooted in a flawed usability objective. The number and depth of these elements should be determined by their relevance to the visitors themselves. Sometimes those paths, those choices, dramatically exceed the number seven. Sometimes they don’t.
Seven is a wonderful number, but don’t let it keep you from designing a persuasive Web site.
